linux-kernel - Re: [PATCH v5 2/3] PCI: qcom: Restrict pci transactions after pci suspend

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Date:   Mon, 8 Aug 2022 14:12:22 -0500
From:   Stephen Boyd <swboyd@...omium.org>
To:     Krishna chaitanya chundru <quic_krichai@...cinc.com>,
        helgaas@...nel.org
Cc:     linux-pci@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mka@...omium.org,
        quic_vbadigan@...cinc.com, quic_hemantk@...cinc.com,
        quic_nitegupt@...cinc.com, quic_skananth@...cinc.com,
        quic_ramkri@...cinc.com, manivannan.sadhasivam@...aro.org,
        dmitry.baryshkov@...aro.org, Jingoo Han <jingoohan1@...il.com>,
        Gustavo Pimentel <gustavo.pimentel@...opsys.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Stanimir Varbanov <svarbanov@...sol.com>
Subject: Re: [PATCH v5 2/3] PCI: qcom: Restrict pci transactions after pci suspend

Quoting Krishna chaitanya chundru (2022-08-03 04:28:53)
> If the endpoint device state is D0 and irq's are not freed, then
> kernel try to mask interrupts in system suspend path by writing
> in to the vector table (for MSIX interrupts) and config space (for MSI's).
>
> These transactions are initiated in the pm suspend after pcie clocks got
> disabled as part of platform driver pm  suspend call. Due to it, these
> transactions are resulting in un-clocked access and eventually to crashes.

Why are the platform driver pm suspend calls disabling clks that early?
Can they disable clks in noirq phase, or even later, so that we don't
have to check if the device is clocking in the irq poking functions?
It's best to keep irq operations fast, so that irq control is fast given
that these functions are called from irq flow handlers.